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Toyota Prius that has been outdoors and not driven for 2 years has extremely rusty disc brake rotors. Sorry, I don't have any current photos or access to the vehicle.

The rotors and pads were satisfactory (normal levels of rust on the rotors) before this 2 year period.

The rotors and pads do not need to be replaced due to wear, but the mechanic (who seems to hopefully be the rare trustworthy mechanic) is recommending replacing all the pads and machining the rotors due to the severe rust.

The mechanic has said he is willing to try to drive the vehicle a little to see if that takes care of the rust. But if not, he provided a large quote to replace the pads and machine the rotors.

Besides driving the vehicle to try to wear the rust off, or machining the rotors and replacing the pads, are there other possible solutions/tips?

Also, obviously rotors rust, but do modern brake pads rust too? If not, is there any reason to replace them (they are not worn)?

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    I'd just run it, but that's a personal choice that no shop would ever recommend. Partly for safety, but mostly because they sell brake services. It'll grind for a bit, but probably will work just fine. After a short while it'll look clean and pretty again. The mechanic you went to is seemingly offering to do this for you.
    – user58368
    Commented Oct 15, 2023 at 20:41
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    Any chance you could provide some useful pictures? The mechanic looking at your vehicle has a much better vantage point than strangers on the Internet reading text. Overall, it sounds like your budget is tight so just get the rotors machined and see how it feels. As a shade-tree mechanic I would likely replace the rotors, pads, and calipers at this point but that would only cost like $800 in parts for my car; YMMV.
    – MonkeyZeus
    Commented Oct 16, 2023 at 12:42
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    Also, check out this post regarding rusty brakes; mechanics.stackexchange.com/questions/44547/…
    – MonkeyZeus
    Commented Oct 16, 2023 at 12:43
  • The pads (friction surfaces) probably haven't rusted, but the metal backing to which the friction material attaches may have rusted. One big detail not given here is where in the world do you live? In some parts of the US, "pad jacking" is an issue - this is where the backing rusts between the backing & friction material and starts to push the friction material off the pad. If left long enough, the friction material can be ripped right off the backing while attempting to brake - Bad Thing™. In other parts of the country, that's unheard of...
    – FreeMan
    Commented Oct 17, 2023 at 12:39

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Repair shop liability issues dictates SAFETY FIRST. Brake repairs are safety issues so there's no cheap economical repair. However, you can, if possible, seek out another repair shop and ask for an estimate. As a rule, rotors and brake pads wear into each other and invariably create a slight taper from hub to outer perimeter and sometimes warp, described as runout on rotors. If rotors are serviceable with machining, new pads are recommended because the original pads have a slight taper that can't be seen by the naked eye. If you can't see 0.002" of runout on worn rotors, you may not feel it as a pulsating brake pedal. Worn (tapered) brake pads may or may not be seen on brake pads and reusing them on machined rotors will not seat properly, creating loss of braking effectiveness. In effect, machined rotors with old brake pads is a recipe for unsafe braking. You also have the choice to replace rusted rotors with new ones, along with new brake pads. And, unavoidably, flushing and bleeding the brake system is recommended every time brakes are replaced. Your safety is important. There's no price for safety if you consider less than correct brake repairs.

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    Thank you for your detailed answer. There are quite a few details in it of which I was not previously aware. Your advice differs from that provided by Jupiter, but it sounds like the classic "what's safest vs. what's cheapest" decision. It's always best to choose safety when it comes to motor vehicles, but it's going to hurt financially. C'est la vie. Commented Oct 15, 2023 at 22:16
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    If you want to be 100% safe, don't drive at all. I'm just saying, a measure of danger is acceptable (within the bounds of the law and good sense).
    – Matthias
    Commented Oct 16, 2023 at 0:50
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Rust on rotors obviously is normal, and normal braking will clean this surface rust off in a short time. But after two years of sitting, it's very possible or probable that the rust has penetrated too far into the rotors surface to get away with that. The rotors probably need turned. Pads should be fine, but they may be worn to the point that they may not need replaced yet, but they may need to be replaced in the near future, so the mechanic may be trying to save another service call in the near future. If this is a trustworthy mechanic, as you say, it's probably best to follow his advice. If you're skeptical get a second opinion. You may find one that you trust more.

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    Thank you for the very helpful answer. I didn't realize the rust could possibly penetrate that far. Your advice differs from that provided by F Dryer, but it sounds like the classic "what's safest vs. what's cheapest" decision. I'm hoping that when the mechanic drives the vehicle he will find the rust is just on the surface and is removed. If not, I'll get mentally prepared for the expense of replacing what he recommends. Commented Oct 15, 2023 at 22:23
  • Extreme rust creates "pits" in metal, reducing the surface in contact with the brake pads. I'd feel the rotor with my fingers and drive it a little to get a feel for it.
    – Matthias
    Commented Oct 16, 2023 at 0:54
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    Pads are cheap, so I would change them whenever doing anything to the rotors anyway. When everything is dismantled it's quick to swap, so only material cost.
    – vidarlo
    Commented Oct 16, 2023 at 10:49
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Even two years of rust will not have degraded the rotors in any significant way. You might get a bit of pitting but that will actually help braking performance - just like more expensive dimpled discs.

Similarly, the metal backing of the pads will not have degraded in any meaningful way. It is unlikely that the friction material of the pads will have degraded, because pads can easily last more than two years in light usage, so the material is unlikely to degrade in that time.

In summary, drive the car and do a lot of hard braking. That will clean surface rust from the rotors and will bed in the pads. I will be very surprised you have any issues at all. If the braking feels fine after this bedding-in then they are good.

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It depends whether there will be vibrations when you remove the rust or not. If so, you should remove at least the rotors. The best way would be to machine the rust off - in that case you may get an even surface, if not possible, drive it then.

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